1. Field of the Invention
The field of the present invention is the monitoring of communications link quality and performance.
2. Description of the Invention
Data communications links are sometimes required to operate reliably in remote highly stressed environments, such as, for example, space vehicles and depolyable probes employed in planetary exploration missions, communications satellites and other space vehicles providing communications links to ground stations and the like. The link may be disturbed by such phenomena as amplitude and phase scintillation, atmospheric absorption, wind gusts and turbulence, probe or spacecraft gain, oscillator drift, Doppler effect, and Doppler rate and noise variations.
For relay repeaters located at remote locations, which receive, demodulate and then retransmit signals to another communications station, there is typically no opportunity to directly measure parameters indicative of the quality of the received signal and the repeater receiver performance, as there would be if the communications link and receiver were accessible for direct measurements, e.g., in a laboratory setting.
Such remote receiver equipment may typically employ feedback loop operation to acquire, track and demodulate the incoming frequency or phase modulated data signal. The demodulated data is then modulated onto a transmit carrier transmission to another station, for example, a ground station.
It is desirable to obtain complete knowledge of the remote receiver status during its demodulation operation so that the link environment disturbances, the receiver tracking performance, and the data detection performance can be understood and quantified. If the repeater station receiver were located in a laboratory, direct measurements could be made to determine, e.g., of such parameters as the incoming signal amplitude, the RMS noise variation and the noise power in the received signal. For many remote relay receivers it is not possible to perform such direct measurements.
It is, therefore, an object of the present invention to provide a means for determining remote communication link quality and receiver performance.
Another object of the invention is to provide a measurable data set of parameters which can be transformed into the derived data set which characterizes the communications link quality and dynamic receiver performance.
Yet another object of the invention is to provide a set of digital processor algorithms adapted to transform the measured data set into the derived data set.